Primary stage for hydraulic distributor



May 16, 1967 R. LUCIEN 3,319,950

PRIMARY STAGE FOR HYDRAULIC DISTRIBUTOR Filed Feb. 18, 1965 3Sheets-Sheet 1 i Y I W I 6 4 7 5 l i I l May 16, 1967 R. LUCIEN PRIMARYSTAGE FOR HYDRAULIC DISTRIBUTOR 3 Sheets-Sheet 2 Filed Feb. 18, 1965 J\\\N| m kw R k m. fi M wm N W .7 MN w .wv u m mv ax w m EN mm b mm Wm QQN m GE y 6, 1967 R. LuclEN 3,319,950

PRIMARY STAGE FOR HYDRAULIC DISTRIBUTOR Filed Feb. 18, 1965 3Sheets-Sheet 5 United States Patent 3,319,950 PRIMARY STAGE FORHYDRAULIC DHSTRIBUTGR Rene Lucien, 56 Blvd. Maillot, Neuilly-sur-Seine,France Filed Feb. 18, 1965, Ser. No. 433,758 Claims priority,application France, July 17, 1961, 868,053, Patent 1,302,520 7 Claims.(Cl. 267-1) This application is a continuation-in-part application of myearlier application, 'Ser. No. 164,094 filed an. 3, 1962, now abandoned.

This application relates to improvements in hydraulic distributors.

More particularly, the present invention relates to hydraulicdistributors with two stages, of the type in which the primary stagecomprises a torque motor, the rotor of which is connected by a rigidshaft operable in rotation, to a blade controlling the flow-rate of twoor four jets, the said rigid shaft being in turn mounted in the interiorof a torsion tube insuring the threefold function of a support, ofapplying a torsion restoring force, and of sealing the chamber of thejets and the torque motor.

In these devices, especially when they have two jets, it is necessary,for the regularity of operation, to eliminate or neutralize the shearstresses due to the jets, since these stresses are liable to cause astray bending of the torsion tube.

A similar problem arises also in connection with the elimination of theeffect of parasitic vibrations to which the blades may be exposed.

Various structures have been proposed, which may be capable of meetingthe general problem explained above. But when these structures, inaccordance with present requirements of the art, are to havesubstantially reduced dimensions, they are no longer able to solve theproblem in question, for two reasons each of which has an adverseinfluence on the other. On the one hand, the shear stresses must besuppressed in a particular manner, owing to the very reduction of thedimensions of the structural members while on the other hand, certainknown constructions, which already extend the field of use toward smalldimensions by locally reducing the end sections of said rigid shaft,suddenly and abruptly cease to be physically realizable, as will beshown below.

More precisely, the invention provides a field of use extending moreminiaturization to micro-miniaturization. For example, the torque motoris electrically controlled and is actuated by a current of the order ofmilliamperes, while the displacement of the blade with respect to one ofthe jets is of the order of hundredths of a millimeter. The diameter ofthe rigid shaft is of the order of fivetenths of a millimeter. It goeswithout saying that structural configurations of the above size excludefrom the outset the well known use of ball bearings (also excluded dueto friction) for supporting the rigid shaft, and yet, said shaft must bemounted, at each of its ends, both rigidly with respect to fiexure andas flexibly as possible in rotation (for very small angles).

In order to meet these two essential requirements, it is known in US.Patent 2,835,265 to locally reduce, by machining, the section of therigid shaft adjacent its end. It will be noted that, in the field of useprovided by the invention, the diameter of the rigid shaft is of theorder of five-tenths of a millimeter and that a machining for reducingthe diameter appreciably and locally over about two millimeters oflength is impossible in ractice. For example, it is impossible to avoidthe notch effect and the concomitant risk of rupture due to stressconcentration. It is also known in US. Patent 2,905,871 to locally forma shape of cruciform section in the rigid shaft adjacent its end. Such acruciform section, when employed in the field of use provided by theinvention, would require that the thickness of the arms of the cross beless than one-tenth of a millimeter, which is impossible to realizelocally over about two millimeters of length of a shaft of aboutfive-tenths of a millimeter in diameter. In particular, the relativevalue of the minimum tolerances necessary for such machining becomeunattainable. On the other hand, it will be noted that the above twopatents necessarily employ the same material for the rigid shaft and forits reduced or cruciform section. The shaft must have a relatively highmodulus of elasticity and this is inconsistent with the high torsionalflexibility required at the reduced and cruciform sections.

In view of the foregoing, it is an object of the invention to provide astructural configuration of the primary stage of a torque motor, whichpermits elimination of the shear stresses and insures insensibility tovibrations by means which are compatible with the reduction of thedimensions in the field defined by the above-mentioned approximatevalues.

In accordance with the invention each end of the rigid shaft is securedby a rod of relatively small dimension in relation to those of the rigidshaft, said rods being embedded in the ends of the rigid shaft and infixed structure, said rods being constituted of a material having acomparatively low modulus of elasticity.

It will be noted that in accordance with the invention the rigid shaftis constituted of a material having a high modulus of elasticity whilethe rods are of low modulus of elasticity which enables obtainingtorsional flexibility at the ends of the shaft which is otherwise rigidwhereby there is avoided the above-mentioned inconsistency in the knowndevices.

Further advantages of the invention will become more clearly apparentfrom the description which follows with reference to the accompanyingdrawing given by way of non-restrictive example, wherein:

FIGURE 1 is a diagrammatic axial section on a very much enlarged scaleof the rotor of the primary stage of a distributor according to theinvention;

FIGURES 2 and 3 are axial sections taken along lines IIII and III-III,on an enlarged scale, of a distributor according to the invention inwhich the secondary stage is diagrammatically outlined but not shown indetail; and

FGURES 4 and 5 are cross-sections taken along lines IVIV and VV at thelevel of the electromagnetic blade and at the level of the hydraulicblade respectively.

FIG. 1, which relates to a primary stage with two jets, shows a magneticblade 1 adapted for oscillating about the axis XX in the air-gaps of amagnetic circuit under the elfect of the control currents passingthrough two windings (not shown). Said magnetic blade is coupled by arigid shaft 2 to the hydraulic blade 3, the extremities of which arelocated in front of the two jets 4 and 5 respectively, at whichterminate the piping systems serving the secondary stage (not shown).The torsion tube 6 surrounds the rigid shaft 1 and is secured, at one ofits extremities, in the flange or fixed structure 7, or alternately itforms an integral portion of said structure. A screw 8 joins togetherthe magnetic blade 1, the rigid shaft 2, and the torsion tube 6.

This type of primary stage operates as follows:

When a variation in current is produced in one of the windings, anelectromagnetic couple force is applied to the blade 1, which causes thesame to rotate against the action of the elastic restoring force of thetorsion tube 6. The rotation of blade 1 causes rotation of tube 6 at theend thereof opposite fixed structure 7, which thereby also causesrotation of shaft 2 by virtue of the connection provided by screw 8. Therigid shaft 2 rotates the blade 3 which causes this blade to thusapproach one of the jets while moving away from the other. Inconsequence, the pressure losses in the pipings terminating at thesejets become unbalanced, and this results in a differential controlpressure at the secondary stage. It is essential according to theinvention that the angular rotation which the blade 3 undergoes must bein precise relationship wtih the magnetic blade 1. Hence, therequirement for substantial rigidity of the shaft 3. However, at thesame time it is essential that the shaft 2 have as high a torsionalflexibility as possible.

According to the invention, two rods 9 and 10 are each fixed, on the onehand, in the extremities of the rigid shaft 2 and, on the other hand, inthe fixed portions 11 and 12 of the stationary structure. The rods mayalso be fixed by brazing. They are of small diameter so as to offer onlya small stiffness in torsion, while they are of small length in order tohave a great rigidity in bending.

Moreover, since it is necessary, in order to obtain maximal dynamicperformance, that the stiffness in torsion of each rod 9 and 10 be assmall as possible, it is expedient that the material of said rods have avery low modulus of elasticity whereby the rods constitute torsionaxles. On the other hand, the rigid shaft 2 which firmly connects themagnetic blade 1 and the hydraulic blade 3 has a relatively smalldiameter, since said diameter is dictated by the size of tube 6 withinwhich it is accommodated, said torsion tube 6 being in turn, of a smalldiameter in order to provide great flexibility in torsion. But in spiteof said small diameter, the rigid shaft 2 must be rigid in torsion, inorder to prevent an angular displacement of one blade in relation to theother, which would bring about a loss of efficiency in the control andmight introduce objectionable parasitic natural frequency. It istherefore necessary that the rigid shaft 2 be constituted of a materialhaving as high a modulus of elasticity as possible. As already statedabove, the structural arrangements in US. Patents 2,835,265 and2,905,871 are not applicable to the present device because these patentsemploy the same material for the rigid shaft and for its reduced orcruciform sections. In contrast thereto, the device of the invention isconstructed and arranged to employ different materials for the rigidshaft 2 and for the rods 9 and 10 to enable the shaft and the rods tosatisfy mutually distinguishing requirements. By way of example, therigid shaft 2 may be constituted of tungsten carbide steel having amodulus of elasticity, E=60,000, whereas the rods 9 and 10, areberyllium bronze whose modulus of elasticity, E=l3,000. Thus, it becomespossible to make the shaft of material which is more than four times asrigid as the torsion axles, whereby said axles may be relativelytorsionaliy flexible while the shaft is torsionally rigid.

It will further be noted that the invention offers with respect toexternal forces the same rigidity in bending in all directions and that,moreover, the system is very resistant to all stray shear stresses.

In FIGS. 2-5 there is shown a distributor whose primary stage isconstructed in accordance with the invention as above described. Thesame members are designated with the same reference numerals as alreadydescribed in connection with FIG. 1. The distributor comprises asecondary stage 21, which does not form part of the invention and whichwill therefore not be described in detail. Said secondary stage 21,which is only diagrammatically outlined in FIGS. 2 and 3, may be of anyknown type which is capable of being controlled by the difference of thehydrodynamic pressure drops at the jets 4 and 5 as controlled by thehydraulic blade 3. Above the secondary stage 21 the distributor 20comprises a plate 22, a plate 23 which is recessed in its center, and anupper platen 23, all of which are assembled by centering pins 25 andscrews 26 (FIGS. 4 and S). The inner space defined by the members 22,23, and 24, is made fluid-tight by the seals 27, to form a hydraulicchamber 28, which accommodates the jets 4 and 5 and the hydraulic blade3. Openings 29 and 30 (FIG. 4) supply the jets 4 and 5 respectively, andan opening 31 evacuates the hydraulic chamber 28 (FIG. 5). On the upperplaten 24, two screws 33 hold the stator 34 of the torque motor (FIG.3). Said stator is formed, in conventional manner, by two permanentmagnets 35 and two coils 36 defining two airgaps 37 controlling themagnetic blade 1 (FIG. 4). Rigidly fixed in the upper portion of thestator 34 is the member 11 which holds the rod 10 of the rigid shaft 2.As already stated, slightly below the upper rod 16, a screw 8 joinstogether the rigid shaft 2, the torsion tube 6, and a tubular extension39 of the magnetic blade 1. The lower end of the torsion tube is heldrigidly by a flange 7 fixed in the upper platen 24. At the lower portionof the rigid shaft 2, the rod 9 is held by a member 12 fixed in a gap 41below the upper platen 24 by two screws 42 (FIG. 3).

It must be emphasized that the device for suppressing or minimizingshear stresses according to the invention offers an advantage of aconstructive nature in addition to its fundamental functional advantagesalready indicated. It will be seen that the torsion tube 6 extendswholly to one side only of its flange or base 7. For the same overallsize of the apparatus and for the same thickness of the tube wall, thisenables the tube to be made longer and therefore more flexible intorsion, which is favorable to the dynamic behavior of the apparatus.

As compared with known primary stages of similar type, the deviceaccording to the invention possesses the superiority of permitting thetorsion tube to operate exclusively in pure torsion and of making itpossible to obtain results which are more uniform and more comparablewith each other than when the effect of torsion is combined with shearstresses, the characteristics of the stage being very greatly improvedfor that reason.

Finally, as compared with certain of these known primary stages, thedevice according to the invention also offers the advantage that it doesnot introduce either friction or hysteresis phenomena by virtue of thefact that the roclls 9 and 10 operate in torsion and constitute torsionax es.

Numerous modifications and variations of the illustrated embodiment willbecome readily apparent to those skilled in the art without departingfrom the scope and spirit of the invention as defined in the attachedclaims.

What is claimed is:

1. In a hydraulic distributor having two stages, one of which isconstituted by a torque motor; a rigid shaft having opposite ends, saidtorque motor being rigidly connected to said shaft, a blade rigidlyconnected to said shaft at a location spaced from said torque motor andcontrolling the other of the stages of the distributor, a torque tubeencircling said shaft and having one end terminating at a locationbetween the torque motor and the blade, said torque tube being fixedlysupported at said one end externally of said shaft, said torque tubehaving an end remote from said one end, means fixedly connecting saidtorque tube at said remote end to the shaft, and a pair of separate rodseach of circular section of substantially smaller diameter and lengththan the shaft, said rods each having one end fixedly secured externallyof said shaft and an opposite end coaxially and fixedly secured to arespective end of the shaft to constitute torsion axles for said shaftand permit solely torsional deflection of said shaft.

2. A distributor as claimed in claim 1, wherein said shaft isconstituted of material having relatively large torsional stiffness,said rods being constituted of material having substantially littletorsional stiffness.

3. In a distributor as claimed in claim 1 wherein said torque tube andmotor are secured to the shaft at one of the ends thereof, the saidblade being secured to said shaft at the other of the ends thereof.

4. In a distributor as claimed in claim 2 wherein the stiffness of thematerial of the shaft is at least four times as great as that of therods.

5. In a distributor as claimed in claim 1 wherein said rods are embeddedat the said opposite ends thereof in the ends of the rigid shaft.

6. In a distributor as claimed in claim 2 wherein the shaft isconstituted of tungsten carbide steel and the rods are beryllium bronze.

7. In a distributor as claimed in claim 1 wherein said shaft has adiameter of about 0.5 mm. and said rods have a diameter of 0.1 mm.

References Cited by the Examiner 5 UNITED STATES PATENTS 2,835,2655/1958 Brandstadter l3782 2,905,871 9/1959 Martin 3l7l71 X ARTHUR L. LAPOINT, Primary Examiner. 10 R. M. WOHLFARTH, Assistant Examiner.

1. IN A HYDRAULIC DISTRIBUTOR HAVING TWO STAGES, ONE OF WHICH ISCONSTITUTED BY A TORQUE MOTOR; A RIGID SHAFT HAVING OPPOSITE ENDS, SAIDTORQUE MOTOR BEING RIGIDLY CONNECTED TO SAID SHAFT, A BLADE RIGIDLYCONNECTED TO SAID SHAFT AT A LOCATION SPACED FROM SAID TORQUE MOTOR ANDCONTROLLING THE OTHER OF THE STAGES OF THE DISTRIBUTOR, A TORQUE TUBEENCIRCLING SAID SHAFT AND HAVING ONE END TERMINATING AT A LOCATIONBETWEEN THE TORQUE MOTOR AND THE BLADE, SAID TORQUE TUBE BEING FIXEDLYSUPPORTED AT SAID ONE END EXTERNALLY OF SAID SHAFT, SAID TORQUE TUBEHAVING AN END REMOTE FROM SAID ONE END, MEANS FIXEDLY CONNECTING SAIDTORQUE TUBE AT SAID REMOTE END TO THE SHAFT, AND A PAIR OF SEPARATE RODSEACH OF CIRCULAR SECTION OF SUBSTANTIALLY SMALLER DIAMETER AND LENGTHTHAN THE SHAFT, SAID RODS EACH HAVING ONE END FIXEDLY SECURED EXTERNALLYOF SAID SHAFT AND AN OPPOSITE END COAXIALLY AND FIXEDLY SECURED TO ARESPECTIVE END OF THE SHAFT TO CONSTITUTE TORSION AXLES FOR SAID SHAFTAND PERMIT SOLELY TORSIONAL DEFLECTION OF SAID SHAFT.